Supporting means for electrical coils in electrical apparatus



P. NARBUT 3,170,131 SLYIPPORTING MEANS FOR ELECTRICAL cons IN ELECTRICAL APPARATUS 2 Sheets-Sheet 1 Fig I Feb. 16, 1965 Filed Aug. 23, 1962 INVENTOR Poul Norbuf ATTORNEY WITN E5568 6% SWMQMQX Feb. 16, 1965 P. NARBUT 3,170,131

SUPPORTING MEANS FOR ELECTRICAL COILS IN ELECTRICAL APPARATUS Filed Aug. 23, 1962 2 Sheets-Sheet 2 24 Fig.2.

United States Patent Office 3,170,131 Patented Feb. 16, 1965 This invention relates to electrical apparatus, such as transformers, and more particularly to a system for providing mechanical support to a shell form transformer coil.

In the past, one practice has been to mechanically support the coils of a fluid insulated shell form transformer principally through the use of solid insulation in the form of prcssboard channels, angles, washers or the like. This practice has the disadvantage, particularly when a gas is the principal insulating medium, of partially displacing the gas; as is well known to those skilled in the art the remaining gas clearances are then subject to higher voltage stresses and the corona and breakdown voltages are lowered.

It is an object of this invention to provide a new and improved method of supporting the coils of a shell form transformer.

It is a more particular object of this invention to provide a new and improved method of supporting the coils of a shell form transformer which uses a minimum of solid insulation, so disposed as to make better use of the available insulation clearances.

Other objects of the invention will in part be obvious and will in part appear hereinafter.

Briefly, the present invention accomplishes the above cited objects by providing metal, vapor or gas inflatable, cushion means or pads to compress the coil stack. More specifically, the inflatable cushions are placed between coil sides and the core on one side of the coil stack to exert a compressive force perpendicular to the coil stack that will prevent movement or separation of the coils due to gravity, handling, or mechanical stresses caused by overloads or short circuits.

For a more thorough understanding of the invention, reference may be had to the accompanying drawings, in

t which:

FIG. 1 shows a vertical cross section of a shell form transformer equipped with the supporting cushions; and

FIG. 2 shows a transverse horizontal cross section of one coil of the shell form transformer of FIG. 1 and the associated supporting cushion taken along plane II-II.

Referring now to FIG. 1, there is illustrated an electrical apparatus, more specifically a transformer comprising a shell form core 24 within which there is disposed a group of coils 26, with each coil having flat sides which are disposed adjacent one another to form a continuous stack Steel end frames 58 are provided to enclose the core 24 and coils 26, with the core 24 and coils 26 being disposed in a suitable enclosure or casing 25. Between the core 24 and the coils 26 gas or vapor inflatable pads 16, 18, and 22, such gas or vapor inflatable pads 16, 18, 20 and 22 may be coated with an protection against lateral move- A plurality of pads are used rather a safety factor to maintain compression of the coils 26 despite a leak in one or more of the pads, and for ease of assembly.

The inflatable pads 16, 18, 20 and 22 may be fitted with flexible gas conduits 14 and connections 12 if it is desired to control and meter the gas or vapor pressure in the inflatable pads 16, 18, 20 and 22 from the outside of the ment of the coils 26. than one large pad as transformer 10 or make up any gas or vapor loss due to leakage.

Referring to FIG. 2, there is illustrated a view of the transformer of FIG. 1 showing a transverse cross section of a portion of the coil assembly body 26 taken at plane IIII. The coil assembly 26 is comprised of a low voltage coil 37 divided into two groups and a high voltage coil group 38.

The lower group of low voltage coil sections 37 in FIG. 2 is comprised of electrical coils such as 39. These electrical coils 39 are separated by electrically insulating outside of washer 41 the inflatable cushion 22. Theinfiatable metal cushion 22 is placed at one end 2 is substantially the same as the above-described lower Between the aforementioned spaced apart groups of low voltage coil 37 is high voltage coil group 38. This coil group comprises a plurality of high voltage electrical coils such as 42. The high voltage coils, such as 42, may be separated by electrically insulating washers or sheets such as 44, and spacers 45. Static plates 46 and 48 may be used to separate the high voltage coil group 38 from the spaced apart low voltage coil sections 37. The static plates 46 and 48 may be separated by electrically insulating spacers 43.

The vapor or gas inflatable pad 22 exerts a compressive force between the coil assembly 26 and the transformer core 24, to prevent any movement or momentary separation of the parts of coil assembly 26.

The inflatable pads or cushions 22 may be constructed of welded sheet metal or of flattened thin Wall metal pipe.

to 250 psi. of pressure would compress the coil stack 26 sufiiciently; however, the pads were tested to 700 p.s.i. without leaks.

by the inflated pad 22 is possible, of any solid insulation support in the electrically highly stressed areas between the edges of the high voltage static plates 48 and the core 24, where such solid insulation would be particularly detrimental. On the other hand, placing the supporting spacers 43 between the static plates 48 and 46, and confining them to this region of the rela- '3 a tively uniform electric field, does so without any appreciable field distortion, and, hence, without an appreciable detriment to the dielectric strength of the available electrical clearances.

Another advantage of the described arrangement is the mechanical strength of the assembly. By the proper design of the gas or vapor pressure in the inflatable cushions 16, 18, 20, 22, the coils at all times will be under adequate compression to prevent any displacement Whether this be due to the shipping or the short circuit stresses. It is to be understood that the outward force developed by the inflatable cushions w'll be confined by the core 24 and the end frames 58. Normally, these structures are adequate to meet this requirement without a radial modification of design.

It should be noted that if the cushions 16, 18, 20, and 22 of FIG. 1 are not sealed after inflation the flexible gas conduits 14 may be brought from the inflated pads or cushions to the outside of the transformer tank and connected through suitable connecting means 53 to a small accumulator or gas reservoir 51 with a pressure gauge.

As a still further modification, the accumulator or gas reservoir 51 may be charged with a suitable liquefied gas to create the required gas pressure. If the gas is chosen to give the desired vapor pressure at the temperature of the accumulator 51, and the variation of the accumulator temperature is small, the pressure in the pads will vary but slightly regardless of thermal expansion and contraction of the coils. For example, such gas may be sulfur hexafluoride, which has a fixed vapor pressure of approximately 350 p.s.i. at room temperature. This selfregulation of pad pressure will continue as long as there is an excess of liquefied gas in the accumulator 51.

A further advantage of this modification is that as long as any liquid is present in thegas reservoir, pressure will be maintained in the pads even in the presence of small leaks.

It will, therefore, be apparent that there has been disclosed a means for utilizing the major insulation clearances between the coils and the core of shell form transwhich may be equipped formers to support the coils with a minimum of solid insulation. The supporting means are so arranged as to make an improved utilization of the available insulation clearances.

Since numerous changes, such as adapting the invention to liquid insulated transformers, or core form transformers, may be made in the above-described apparatus, and different embodiments of the invention may be made by those skilled in the art without departing from the spirit thereof, it is intended that all the matter contained in the foregoing description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

I claim as my invention:

1. An electrical transformer comprising, a magnetic core, a plurality of electrical coils disposed in inductive relation with said magnetic core, said electrical coils each having substantially flat sides which are disposed adjacent one another to form a stack of electrical coils, means disposed at one end of said stack of electrical coils compressing said stack with a pressure substantially perpendicular to the flat sides of said electrical coils to maintain said electrical coils in assembled relation by friction forces, said means including a plurality of inflatable containers and supporting structure which exert a predetermined pressure on said stack of electrical coils and supporting structure when inflated with a gaseous medium.

2. An electrical transformer comprising, a magnetic core, a plurality of electrical coils disposed in inductive relation with said magnetic core, said electrical coils each having substantially flat sides which are disposed adjacent one another to form a stack of electrical coils, means disposed at at least one end of said stack of electrical coils compressing said stack with a pressure substantially perpendicular to the flat sides of said electrical coils to maintain said electrical coils intermediate the ends of said stack in assembled relation by friction forces, said means including a plurality of inflatable, gas tight containers and supporting structure which exert a predetermined pressure on said stack of electrical coils and sup porting structure when inflated with an electrical insulat ing gaseous medium.

3. An electrical transformer comprising, a casing, a magnetic core disposed within said casing, a plurality of electrical coils disposed in inductive relation with said magnetic core, said electrical coils each having substantially flat sides which are disposed adjacent one another to form a stack of electrical coils, first means disposed at at least one end of said stack of electrical coils adjacent said magnetic core and compressing said stack with a pressure substantially perpendicular to the flat sides of said electrical coils to maintain said electrical coils in assembled relation by friction forces, said first means including a plurality of inflatable containers which exert a predetermined pressure on said stack of electrical. coils and said magnetic core when inflated with a gaseous medium, and second means including a reservoir and conduit means for providing a gaseous medium at a predetermined pressure to said first means.

4. An electrical transformer comprising, a casing and end frames, a magnetic core disposed within said casing, a plurality of electrical coils disposed in inductive relation with said magnetic core, said electrical coils each having substantiallyflat sides which are disposed adjacent one another to form a stack of electrical coils, solid electrical'insulation disposed at the ends'of said stack of electrical coils, a gaseous electrical insulating medium disposed in said casing to surround said magnetic core and electrical coils, first means disposed at at least one end of said stack of electrical coils compressing said stack with a pressure substantially perpendicular to the flat sides of said electrical coils to maintain said electrical coils in assembled relation by friction forces, said first means including a plurality of inflatable containers which exert a predetermined pressure on said stack of electrical coils, said magnetic core, said end frames, and said solid electrical insulation, when inflated with a gaseous medium, and second means including a reservoir and conduit means for providing a gaseous medium at a predetermined pressure to said first means.

References Cited in the file of this patent UNITED STATES PATENTS 

1. AN ELECTRICAL TRANSFORMER COMPRISING, A MAGNETIC CORE, A PLURALITY OF ELECTRICAL COILS DISPOSED IN INDUCTIVE RELATION WITH SAID MAGNETIC CORE, SAID ELECTRICL COILS EACH HAVING SUBSTANTIALLY FLAT SIDES WHICH ARE DISPOSED ADJACENT ONE ANOTHER TO FORM A STACK OF ELECTRICAL COILS, MEANS DISPOSED AT ONE END OF SAID STACK OF ELECTRICAL COILS COMPRESSING SAID STACK WITH A PRESSURE SUBSTANTIALLY PERPENDICULAR TO THE FLAT SIDES OF SAID ELECTRICAL COILS TO MAINTAIN SAID ELECTRICAL COILS IN ASSEMBLED RELATION BY FRICTION FORCES, SAID MEANS INCLUDING A PLURALITY OF INFLATABLE CONTAINERS AND SUPPORTING STRUCTURE WHICH EXERT A PREDETERMINED PRESSURE ON SAID STACK OF ELECTRICAL COILS AND SUPPORTING STRUCTURE WHEN INFLATED WITH A GASEOUS MEDIUM. 